Intraocular surgical procedures require three or more sclerotomies for enabling the introduction into an eye's interior of a light probe and a surgical instrument and the connection to either a supply line to a source of pressurized air or an irrigation line to a source of physiological liquid for maintaining normal intraocular pressure despite a continuous undesirable leakage from the eye's interior through the sclerotomies. In view of physiological considerations, the diameter of a sclerotomy is limited to between about 1 mm-1.5 mm.
U.S. Pat. No. 4,795,426 describes a tip portion for a catheter placement cannula, the tip portion being in the form of a pair of flexible lips which assume a naturally flattened shape to provide a seal for preventing the backflow of blood or other fluids. To this end, the lips are made of shape retaining memory material of a relatively thick dimension. In view of such a construction, the tip portion is suitable for insertion into a large access port as made in, for example, an abdominal wall, however, it does not lend itself for miniaturization for insertion into a small access port, for example, a sclerotomy.